Timeline:1920
1925 : Month Unknown :: - Walburga Black, mother of Sirius and Regulus is born. (Black Family Tree) :: - Phineas Nigellus Black, the least popular headmaster of Hogwarts ever, dies. (Black Family Tree) : September :: Bob Ogden visits the Gaunt house after the Ministry received information that Marvolo's son, Morfin, had attacked a Muggle (the muggle turned out to be Tom Riddle, Sr. for whom Merope secretly loved). ::: There he encounters the irate Marvolo Gaunt who refuses to admit Morfin has done anything wrong. When Ogden steps in to stop them injuring Merope, he is driven from the house. He returns later with reinforcements, and Marvolo and Morfin are each sent to Azkaban. (Half-Blood Prince) : October :: 4'' - Minerva McGonagall is born. ::: Rowling stated in a 2003 interview with Scholastic that McGonagall was "a sprightly 70" years old. Using that information, we can determine the year in which she was born by subtracting 70 years. If we assume that Rowling was saying that McGonagall was 70 years old at that point in the stories, which was summer of 1995, then she was born in 1925. Interestingly, that would make McGonagall a contemporary of Tom Marvolo Riddle at Hogwarts. ::: The date of October 4th comes from an entry Rowling made on her website. : ''December :: Merope, finally free from her abusive father and brother, bewitches Tom Riddle, Sr. into falling in love with her, most likely with a love potion. (Half-Blood Prince) 1926 : March :: Marvolo Gaunt returns from Azkaban to find Merope gone. ::: He had been given a six-month sentence. Forced to live alone, he withers away and dies sometime within the next two and a half years. (Half-Blood Prince) :: Merope becomes pregnant with Tom Marvolo Riddle ::: Her husband, Tom Riddle, Sr., leaves her very soon afterward - Dumbledore suspects because she stops giving him love potion. The date is deduced from being nine months before Voldemort's birth date. We know Tom Riddle, Sr. leaves her soon afterward because they were only married for "a few months." (Half-Blood Prince) : December :: Merope sells Slytherin's Locket to Borgin and Burkes. ::: Pregnant and desperate for money, she has no idea what it's worth and is only given ten Galleons for it. The locket is later sold to Hepzibah Smith. According to Caractacus Burke, this happened "just before Christmas." (Half-Blood Prince) :: 31 - Tom Marvolo Riddle is born in a London orphanage. :::: Merope, just before dying, requests that he be named after his father, Tom Riddle, Sr., and her father, Marvolo. (Half-Blood Prince) 1928 : September :: Morfin Gaunt returns from Azkaban. ::: He returns after a three-year sentence to find both his father and sister, Marvolo and Merope, dead. He lives alone in the Gaunt house for many years, until Tom Marvolo Riddle returns and frames him for murdering the Riddle family. (Half-Blood Prince) : December :: 6'' - Rubeus Hagrid is born to a human father and the giantess Fridwulfa. (Goblet of Fire) 1929 : ''Month Unknown :: Cygnus Black, father of Bellatrix, Narcissa, and Andromeda Tonks, is born. (Black Family Tree) :: Orion Black, father of Sirius and Regulus, is born. (Black Family Tree)